Normal map rendering blocky shading/ shadows
I couldn't figure out the solution as to why my normal map was giving me such harsh quad shading. I opened it in other programs and determined that the normal map generated from the baked diffuse I used on the rock always contained harsh edges even though the normal map itself doesn't show it.

Instead I found this incredible tool for combining normal maps and used my original baked normal map and combined it with another to give it more texture. The method I used was to open the broken normal map into gimp2, turn it back&amp;white and then use the gimp2 normal map plugin to turn it back into a normal map.

https://www.blendswap.com/blends/view/76176 &lt;&lt;&lt; This is the combine normal map tool I used. Huge thanks to RadCapricorn for uploading this.

Here's my result: 

So agian in bullet points:

-Take broken N-map into Gimp2
-Turn it greyscale and edit contrast according to how much detail you prefer
-Use Gimp2 normal map plugin found here: https://code.google.com/archive/p/gimp-normalmap/downloads and a cute tutorial on how to use it here: https://www.youtube.com/watch?v=8Jdo3ZmtPWk

Then if you want to combine the normal map with your original baked one then:

Use this blend file: https://www.blendswap.com/blends/view/76176

Follow the instructions contained within the blend file itself.

New blender 2.8 shortcut to save images: SHIFT+S (it's no longer F2)